<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #d1{
            width: 50px;height: 100px;background-color: red;
            position: absolute;
            /*通过z-index控制元素的显示层级,值越大显示越靠前*/
            z-index: 1;
        }
        #d2{
            width: 100px;height: 50px;background-color: blue;
            position: absolute;
            z-index: 2;
        }
    </style>
</head>
<body>
<div id="d1">div1</div>
<div id="d2">div2</div>
</body>
</html>